Wietse Venema via Postfix-users:
> hawky--- via Postfix-users:
> > Hi Wietse,
> >
> > we are struggling with t-online.de: As you may know as SMTP client you
> > have to fulfill a bunch of requirements to be able to send mails to
> > t-online.de. From time to time we receive mails from t-online.de, but
> > can't answer.
> >
> > So our idea is, in case the mail comes from t-online.de, we process and
> > delivery the mail but return an (meaningful) error message to the
> > t-online.de SMTP client.
> >
> > This is meant as signal so that huge email provider can't dictate their
> > rules (besides SPF, DKIM, DMARC, etc. what we support) - and should
> > prevent a discussion like: "Just fulfill the requirements..." ;-)
>
> If you want the business from t-online users, play by their rules
> instead of giving you users a poor experience when they respond to
> t-online email.
>
> Otherwise, you could reject t-online email selectively:
>
> smtpd_???_restrictions =
> ....
> reject_unauth_destination
> check_sender_access inline:{
> {t-online.de = reject_unverified_sender}}
> ...
>
> If t-online.de blocks mail from your site, then the sender will
> receive some gibberish that they can pass on to their support people.
https://www.postfix.org/postconf.5.html#smtp_delivery_status_filter
can transform the gibberish.
/etc/postfix/main.cf:
smtp_delivery_status_filter =
pcre:/etc/postfix/smtp_delivery_status_filter.pcre
/etc/postfix/smtp_delivery_status_filter.pcre
/\Qcontact t...@rx.t-online.de for reset\E/ 4.0.0 Sorry, your email cannot
be replied to
(with PCRE, there is no need to escape '.' as '\.' in text between
\Q and \E).
Wietse
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